The invention relates to a filter cartridge according to the preamble part of claim 1 as well as to a condenser according to the preamble part of claim 13.
A filter cartridge as known from EP-A-0 669 506 is provided within a collecting tube or header pipe of the condenser and is sealed and positioned by means of a metallic plug screwed into the insertion opening of said tube. Since said filter cartridge is supported in its operating position under a certain axial load, it simultaneously is backed up by the plug. This is a conventional structural principle of filter cartridge equipped condensers. There is a relatively precisely machined and tight thread connection provided between the plug and the insertion opening. This is expensive. However, since the condenser or the condenser housing during manufacturing, e.g. during soldering, is thermally loaded relatively strong, without the filter cartridge positioned within the header pipe, deformations of the insertion opening might occur so that the plug cannot be screwed in easily later and might not be sufficiently tight. Moreover, further irregularities between the plug and the insertion opening at the threaded connection might result from unavoidable temperature variations and corrosion effects and varying mechanical loads during operation of the condenser. This makes its particularly complicated to remove the plug for a change of the filter cartridge after a long duration use of the condenser. Even if then the plug can be removed in a troublesome way it often cannot be used a second time. Also a new plug then does not fit properly into the insertion opening. This problem might cause expensive and time-consuming re-machining efforts.
It is a task of the invention to provide a filter cartridge as well as a condenser with a filter cartridge, as mentioned above, which are structurally simplified and which allow assembly and disassembly and an exchange of the filter cartridge in a comfortable way.
Said task can be achieved by the features contained in claim 1 and in view to the condenser by the features of claim 11.
Since the plug is a part of the filter cartridge a separate manufacturing of a proper plug is avoided. The plug is mounted in the insertion opening first when also the filter cartridge is inserted. The plug then hermetically seals the insertion opening against the outer environment. Simultaneously the plug takes care of the correct positioning of the cartridge. The plug does not need to be screwed-in so that a threaded connection sensitive to deformation is avoided. The plug, instead, can be pressed in axially and/or secured in position by simple fastening elements.
The dual function plug made from plastic material as or light metal forming a part of the filter cartridge offers the possibility of a simple and comfortable assembly of the cartridge into the condenser, since the plug is introduced or pressed into the header pipe together with the filter cartridge until the filter cartridge and the plug reach their respective and correct positions. The plug, particularly if it is made from plastic material, is able to adapt itself to the shape of the insertion opening, even if the insertion opening should have been de-formed during the thermal treatment of the condenser or condenser housing or de-forms during operation. The necessary tightness is assured permanently. Removal, e.g. for exchanging the filter cartridge, of the plug can be carried out comfortably. The plug seals the collector tube and positions the cartridge.
As the filter cartridge has to be secured in the long header pipe of the condenser in its correct operating position, it is expedient, to provide the filter cartridge with a spacer and to provide the plug directly at said spacer.
Said plug can be connected detachably with the spacer or can be formed unitary with the spacer e.g. from plastic material.
Expediently the plastic or light metal spacer comprising the plug is detachably connected to the housing of the filter cartridge.
In order to achieve a correct positioning of the filter cartridge it is of advantage to support the spacer in the housing of the filter cartridge in a yieldable fashion (to axially pre-load the cartridge).
In an alternative embodiment the plug is provided at the lower end of the housing of the filter cartridge. In this case this is a filter cartridge which is inserted through a lower insertion opening into the header pipe of the condenser and which is positioned by the plug.
In view to manufacturing it is of advantage if the plug is a cylindrical body of plastic material or light metal with in-built sealing grooves and a supporting element like a surface for a securing element Said plug is brought into its sealing position essentially only by axially pressing it into the insertion opening. Sealings provided in said grooves, preferably several O-rings, assure the necessary tightness. The supporting surface bears against the securing element such that the plug and by means of the plug also the filter cartridge remain properly positioned.
For an easy removal of the filter cartridge a gripping flap can be formed on the plug.
Alternatively or additionally a seat socket and a channel for a sensor and/or a charging valve can be formed in said plug, said socket receiving said sensor and/or charging valve.
The housing of the filter cartridge is equipped in the outlet zone with filter material having small pores the sizes of which suffice to retain even the smallest particles. To the contrary, the inlet zone is provided with micro-bores assuring a strong and uniform flow of the refrigerant towards the desiccant charge within the housing. Said micro-bores can be produced far less expensively in an injection mold than to mold a conventional cage-like housing portion. Said micro-bores can be formed by needle-like inserts in the injection mold and during the injection process of the housing. Expediently said needle-like inserts extend perpendicular to the mold separation plane such that they can be positioned stationarily within the form and are pulled out from the product when the mold halves are separated.
In another embodiment, the housing of the cartridge directly is connected to the plug. The housing has openings covered by molecular sieves, and may be provided with a separation sealing lip or O-ring. The desiccant charge is received in a flexible fabric or sieve bag connected to the housing and in flow connection with the interior of the housing.
Said filter cartridge can be assembled easily into the condenser and can be changed at any time through the insertion opening, irrespective where said opening is located. The plug as a part of the filter cartridge is provided at the respective end of the filter cartridge, and consists expediently of plastic material or light metal. The plug is positioned in the insertion opening by an essential axial pushing movement and does not need a threaded connection. The plug maintains its position with the help of the securing element positively engaging into the inner wall of the insertion opening. Said securing element hinders the plug to inadvertently move out from the insertion opening. Said securing element can be a Seeger-ring or C-ring which is available in different sizes and with low costs. Seeger-rings are easy to mount and remove and generate the necessary holding force for the plug in a positive fashion.
In another embodiment said securing element may be a clip or a locking pin extending from outside through said header pipe and said plug. Said securing element can be removed and mounted comfortably and establish a high degree of safety against accidental removable. Said clip or locking pin may be inserted into a lateral shaft provided in the plug such that the plug neither can be pressed inwardly nor can escape from the header pipe. Expediently said clip or locking pin has an insertion end and at its opposite end a holding end. Said holding end positively is supported at the outer side of the header pipe, while another safety element can be inserted into the protruding insertion end. Said safety element may be a spring ring or a spring clip or even a lock. The clip or locking pin can be made of metal or plastic material.
Expediently said clip is formed like an elastic tongue which is flat in lateral direction and has a width smaller than the width of the shaft in the plug and is formed with a bend such that it can be held under pre-load when inserted to more safely secure the plug in its position.
Another embodiment uses a bayonet system for securing the plug in its position. A guiding curve can be provided, e.g. at the inner side of the wall of the header pipe for an engaging element of the plug. In case that said guiding curve is U-shaped the bayonet provides a further safety aspect, because the plug has to be first pressed in for the removing rotation of the bayonet design. However, the plug only can be pressed in if there is no significant pressure within said header pipe. As long as there is residual pressure, the bayonet closure cannot be opened until the pressure has been vented in the conventional way. This protects the car mechanic or the car owner when trying to exchange the filter cartridge with the system under pressure.
Even with a securing ring, e.g. a C-ring, said safety aspect can be provided, assuring that the cartridge cannot be removed inadvertently as long as the system pressure is too high. For that function the header pipe may be formed with an inclined shoulder supporting the plug, and with an axial clearance in the seat groove for the C-ring. An outer counterstay shoulder of the groove is firmly contacted by the C-ring in case of considerable system pressure, hindering to remove the C-ring without first relieving the pressure.